Placeholder in --gdk-debug=FLAGS in --help output
Placeholder in --gdk-no-debug=FLAGS in --help output
Placeholder in --gtk-debug=FLAGS in --help output
Placeholder in --gtk-no-debug=FLAGS in --help output

Current
Lojban:

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Located in
../gdk/gdk.c:238 ../gdk/gdk.c:241 ../gtk/gtkmain.c:461 ../gtk/gtkmain.c:464